Russian President Vladimir Putin has criticised the United States for what he said was its "almost uncontained" use of force around the world.

Washington's "very dangerous" approach to global relations was fuelling a nuclear arms race, he told a security summit in Munich.

Correspondents say the strident speech may signal a more assertive Russia.

The White House said it was "surprised and disappointed" by the Russian president's comments.

"We expect to continue co-operation with Russia in areas important to the international community such as counter-terrorism and reducing the spread and threat of weapons of mass destruction," said Gordon Johndroe, press secretary for the White House National Security Council.

Mr Putin told senior security officials from around the world that nations were "witnessing an almost uncontained hyper use of force in international relations".

What we are talking about here is a very, very sensitive technology, and for that reason we need a high degree of transparency...

"One state, the United States, has overstepped its national borders in every way," he said, speaking through a translator.

"This is very dangerous. Nobody feels secure anymore because nobody can hide behind international law.

"This is nourishing an arms race with the desire of countries to get nuclear weapons."

BBC defence and security correspondent Rob Watson, in Munich, said Mr Putin's speech was a strident performance which may well be remembered as a turning point in international relations.

Iran says it wants nuclear power, not nuclear weapons

US defence secretary Robert Gates, also attending the summit in Munich, said only that the Russian leader had been "very candid".

Democratic Senator Joseph Lieberman said Mr Putin's speech was "provocative", adding that its rhetoric "sounded more like the Cold War".

And Republican Senator John McCain added: "Moscow must understand that it cannot enjoy a genuine partnership with the West so long as its actions at home and abroad conflict fundamentally with the core values of the Euro-Atlantic democracies. In today's multi-polar world there is no place for needless confrontation."

Mr Putin's spokesman Dimitry Peskov said the speech was "not about confrontation, it's an invitation to think".

"Until we get rid of unilateralism in international affairs, until we exclude the possibility of imposing one country's views on others, we will not have stability," he said.

'Power not weapons'

The conference, founded in 1962, has become an annual opportunity for world leaders to discuss the most pressing issues of the day.

Earlier, German chancellor Angela Merkel told delegates the international community was determined to stop Iran getting nuclear weapons.

There was "no way around" the need for Tehran to accept demands from the UN nuclear watchdog, the International Atomic Energy Agency (IAEA), she said.

"What we are talking about here is a very, very sensitive technology, and for that reason we need a high degree of transparency, which Iran has failed to provide, and if Iran does not do so then the alternative for Iran is to slip further into isolation," she said.

Iranian nuclear negotiator Ali Larijani, also at the conference, has been repeating Iran's position that it wants nuclear power, not nuclear weapons.

"We believe the Iranian nuclear dossier is resolvable by negotiation," Mr Larijani was quoted by Reuters news agency as saying on the sidelines of the conference.

European diplomats are hoping to hold informal talks with Mr Larijani at the two-day summit.

It would be their first meeting since the collapse of talks last year and the imposition of limited UN sanctions on Tehran for its failure to stop the enrichment of uranium.